Experimental Study on Thermal Drying Characteristics and Pollutant Discharge Law of Municipal Sludge

doi:10.12141/j.issn.1000-565X.210726

Abstract

Abstract:

With the development of China’s economy and the acceleration of the urbanization process, the amount of municipal sludge has increased sharply. Sludge treatment and disposal has become an urgent problem to be solved. By taking the sludge from a sewage treatment plant as the research object, this paper studied its thermal drying characteristics and pollutant discharge law. In the study, the thermal weight loss experiment was carried out at seven sets of temperatures at 100 ~ 250 ℃ equidistantly with homemade equipment, and the drying properties were characterized by the drying rate and the dehydration rate. It is found that the best temperature for drying is 200 ℃. Moreover, the gaseous pollutants were measured online with a flue gas analyzer. It is found that, besides NH₃ and H₂S, the gaseous pollutants also contain acid gases such as NO, SO₂ and HCl, as well as hydrocarbon components such as CO, CO₂, H₂, C₂H₆ and C₂H₄. The experiment also finds that the temperature being controlled below 200 ℃ is beneficial to inhibit the release of gaseous pollutants. Under the experimental conditions, the drying condensate is high-concentration organic wastewater, the pH values are concentrated in the range of 8.88 ~ 9.17 at 125 ~ 250 ℃, forming a buffer system; the COD increases as the temperature increases, and is up to 16 000.0 mg/L under the experimental conditions. Through the basic fuel characteristics test results of the dried sludge, it can be found that the carbon content and calorific value at 125 ~ 275 ℃ decrease with the increase of temperature, but at 300 ℃, due to the conditions of low-temperature carbonization, both the carbon content and calorific value increase. This provides ideas for the energy conversion of sludge. Combining SEM, BET and other methods to characterize the sludge, it finds that temperature increase can increase the microporous structure of the dried sludge, the structure of sludge becomes loose, so that the sludge can be used as a low-grade adsorbent or building material. The results in this paper provide a new idea for sludge resource utilization.

Key words: sludge drying, pollutant discharge, low-temperature carbonization, microstructure, porous media, waste treatment

CLC Number:

X799.3

LIAO Yanfen, QIU Mengze, CHEN Shunkai, et al . Experimental Study on Thermal Drying Characteristics and Pollutant Discharge Law of Municipal Sludge[J]. Journal of South China University of Technology(Natural Science Edition), 2022, 50(8): 92-101.

Figures/Tables 14

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工业分析结果/%			元素分析结果/%
灰分	挥发分	固定碳	C	H	O^1）	N	S
40.52	54.66	4.82	15.65	3.267	35.683	2.22	2.660

组次	pH值	COD/（mg·L^-1）	组次	pH值	COD/（mg·L^-1）
空白组	6.81	31.6	175 ℃组	9.14	7 200.0
100 ℃组	6.03	460.0	200 ℃组	8.88	12 200.0
125 ℃组	9.17	1 176.0	225 ℃组	9.11	14 000.0
150 ℃组	9.15	2 960.0	250 ℃组	9.13	16 000.0

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